Effects of high selenium and fat supplementation on growth performance and thyroid hormones concentration of broilers

A total of 400, as hatched, broilers were used to investigate the effect of increase of selenium and energy intake on thyroid hormone metabolism, growth and liver fatty acid profile. There were 5 replicates of 4 dietary treatments namely, TA (0.289mg Se per kg diet and adequate energy content), TB (0.583mg Se per kg diet and adequate energy content), TC (0.267mg Se per kg diet and 9% increase of energy content) and TD (0.576mg Se per kg diet and 9% increase of energy content). Diets were isonitrogenous. Zinc L-selenomethionine complex was used to increase Se content and corn oil was used to increase the energy content. The experiment lasted 42 days. Broiler growth performance was not significantly affected by dietary treatments. Liver glutathione peroxidase (GPx) activity increased (P<0.05) in broilers fed high Se and energy diets compared to other ones. Whole blood GPx activity was higher in Se supplemented groups however, it was reduced by age. Thyroid hormone concentrations were unaffected by dietary treatments. A significant increase of linoleic and arachidonic acid concentration (P<0.001) was observed in the liver of broilers fed diets with moderately increased energy content and supplemented with Se compared to those fed diets with moderately increased energy content alone. In conclusion, zinc L-selenomethionine complex and moderate increase of energy content did not affect growth rate or thyroid hormone metabolism but led to increased liver fatty acid content and hepatic GPx activity.